Trial pits
Excavations alongside foundations to expose their depth, type and bearing ground, essential for assessing movement, designing underpinning and confirming conditions before extensions or basements.
Site Investigation
Site Investigation & Opening-Up Works
Intrusive investigation across London, trial pits, opening-up works and inspection of hidden structure to diagnose defects and inform the right repair.
The Short Answer
What site investigation involves
Site investigation is the intrusive, hands-on stage of diagnosis. Where a visual survey cannot confirm what is happening, we physically open up the structure and ground, digging trial pits to expose foundations, opening up walls, floors and finishes, and inspecting the hidden structure beneath. It is how we move from "we think" to "we know": establishing foundation depth and type, ground conditions, the extent of a defect and its real cause, so that any repair, underpinning or extension is designed on evidence rather than assumption.
What We Provide
Intrusive investigation, carried out properly
Targeted, engineer-led investigation that gets the information needed with the least disruption to the building.
Opening-up works
Carefully opening up walls, floors, ceilings and finishes to expose concealed structure, connections and previous alterations so the true condition can be assessed.
Foundation investigation
Establishing foundation type, depth and condition, and the nature of the supporting ground, to inform subsidence assessment, underpinning and new structural loads.
Drainage & ground checks
Checking for leaking drains, soft ground, made ground or tree-root influence that may be driving movement, so the cause is addressed, not just the symptom.
Inspection & recording
Close inspection of the exposed structure with measurements, photographs and notes, recording exactly what is found before anything is reinstated.
Findings & recommendations
A clear write-up of what was found and what it means, with engineer-led recommendations that feed straight into a repair strategy, underpinning design or building works.
Who This Is For
When site investigation is needed
Investigation is worthwhile whenever the cause of a problem, or the make-up of a building, cannot be confirmed from the surface.
- Homeowners
- Developers
- Buyers & sellers
- Architects
- Insurers & loss adjusters
Our Approach
How an investigation runs
Planned to get the answers with the least possible disruption, and reinstated safely afterwards.
1
Scope
Agree what we need to find out and the most targeted way to expose it, with minimal disruption.
2
Open up
Carry out trial pits and opening-up works safely, controlling access, support and temporary works.
3
Inspect
Inspect, measure and photograph the exposed structure, foundations and ground conditions.
4
Reinstate
Make the openings and excavations safe and reinstate them once the information is recorded.
5
Report
Set out the findings, the diagnosis and clear recommendations for repair or design.
6
Act
Feed the findings into a repair strategy, underpinning design or construction works.
Related Services
Services that work alongside site investigation
Investigation usually feeds directly into one of these next steps.
Structural Surveys & Defect Diagnosis
Visual survey and diagnosis, with intrusive investigation where needed.
Learn moreSubsidence & Movement
Assessment of subsidence and movement, informed by trial pits and ground checks.
Learn moreUnderpinning & Foundations
Foundation stabilisation and underpinning, designed on investigation findings.
Learn moreFAQs
Site investigation questions, answered
What is intrusive site investigation?
Intrusive site investigation means physically opening up parts of a building or ground to see what is really there, rather than relying on a visual survey alone. It includes trial pits to expose foundations, opening-up of walls, floors and finishes, and inspection of hidden structure, so the cause of a defect can be diagnosed and the right repair designed with confidence.
What is a trial pit?
A trial pit is a small excavation, usually next to a foundation, that exposes its depth, type and the ground it bears on. Trial pits are commonly used to assess foundations affected by subsidence or movement, to inform underpinning design and to confirm ground conditions before extensions or basements.
Do I need opening-up works before repairs?
Often, yes. Where the cause of cracking, movement or a defect cannot be confirmed from the surface, opening-up works expose the hidden structure so a defect can be diagnosed accurately. This avoids guesswork, prevents over-specifying repairs and gives a sound basis for an engineering-led repair strategy.
Will you make good after investigation?
Yes. We plan investigation works to be as limited and targeted as possible, and trial pits and opening-up are reinstated safely once the necessary information has been recorded. We then provide clear findings, photographs and recommendations you can act on.
Need to find out what's really going on?
Tell us about the building and the problem, and we will advise the most targeted investigation to get you a clear answer.